Diagnostic Inflation of The Knee Joint

Abstract

THE roentgenogram is a diagnostic aid of great value in bone and joint diseases. It reveals and confirms such pathologic changes as clinical medicine is often unable to visualize. In the early years of roentgenographic experience, one was unable to make a diagnosis from X-ray evidence alone. As a result of careful observation and study, however, the radiologist is frequently able to diagnose lesions without the contribution of clinical evidence. With the refinement of instruments added to careful study, the possibilities of diagnosis have become boundless. There are still a large number of conditions where the X-ray findings are exceedingly limited, among which the knee joint figures very conspicuously. This limitation is not due to the fact that the roentgenogram does not reveal the existing pathology, but may be attributed to the lack of our own knowledge in X-ray interpretation of soft tissue changes. Clinical medicine helps to pave the way for X-ray interpretation, but without surgical aid confirming the actual presence of pathology, the existence even of gastric ulcer would not have been as well known as it is to-day. A sufficient number of knees have not been operated upon in obscure conditions to correlate the pathology with the X-ray findings. The hazy outlines and shadows, therefore, mean nothing. We are still unable to disclose, in a large percentage of cases, the presence of a torn cartilage; or to disclose or interpret with a great degree of accuracy the existence of changes in the synovial membranes. In this paper we will deal with derangements of the knee joint which, under ordinary circumstances, present negative findings in the roentgenogram. Soft tissue structures do not readily cast a shadow unless considerable change has taken place, or some medium is introduced into the tissues to outline these structures. Liquids injected into a joint for diagnostic purposes are too irritating, often leading to adhesions, and are absorbed too slowly. Gaseous substances are preferable and therefore oxygen and carbon dioxide should be employed. Carbon dioxide has been used in our series of cases because it is very readily absorbed, producing very little irritation. One must be familiar with the pathology which takes place as a result of internal derangements of the knee and determine if the roentgenogram reveals these changes. The knee joint differs from all other joints in the body in that it is purely a hinge joint, permitting only a small amount of rotation, and that only when the knee assumes the position midway between flexion and extension. This position is often called the “danger zone,” because, when the joint is in this position, injuries take place which are of more serious consequence, namely, displacements and tears of the semilunar cartilages. The anatomical structures which as a rule show no changes in the roentgenogram are the synovial membrane, fat pad and the semilunar cartilages.